1. Field of the Invention
The present invention relates to a heater utilizing fluid frictional heat in which heat is generated in a viscous fluid by shearing to heat a fluid circulating through a heat receiving chamber which is used as a heating source.
2. Description of the Related Art
Hitherto, a heater utilizing fluid frictional heat for use in an automobile heating apparatus is disclosed in U.S. Pat. No. 4,993,377 issued Feb. 19, 1991 to Masato Itakura and its corresponding Japanese Patent, Japanese Patent Application Laid-open No. 2-246823 filed Mar. 21, 1989. In this disclosed heater utilizing fluid frictional heat, a front and a rear housings are fastened together by through bolts in opposite relation to define therein a heat generating chamber and a water jacket, i.e., a heat receiving chamber, around the heat generating chamber. Circulating water is admitted into the water jacket through an inlet port, and circulates in the water jacket, and then flows out of an outlet port to an external heating circuit. A drive shaft is rotatably supported by a bearing unit in the front housing, and a rotor which is rotatable in the heat generating chamber is fixed on the drive shaft to serve as a shear applying portion. Labyrinth grooves are formed in close relation to each other between a wall surface forming the heat generating chamber and an outer surface of the rotor. A viscous fluid such as a silicone oil is placed in a gap between the wall surface forming the heat generating chamber and the outer surface of the rotor.
When the above heater utilizing fluid frictional heat is assembled in an automobile heating apparatus and the drive shaft is driven by the engine, the rotor rotates in the heat generating chamber and the shearing force, being proportional to the number of revolutions of the rotor, is applied to the viscous fluid in the labyrinth grooves. This allows internal energy and frictional heat in the viscous fluid to increase, causing the viscous fluid to generate heat. The high temperature viscous fluid thus heated is heat exchanged with the circulating water in the water jacket, and the thereby heated circulating water flows out to the heating circuit to heat the automobile passenger compartment.
In the conventional heater utilizing fluid frictional heat mentioned above, the rotor has a large diameter relative to its axial length, and therefore generates most of the heat on its front and rear surfaces. Stated in another way, the rotor is configured to have a short axial length, but a large diameter. Recently, however, automobile engine compartments have become very cramped with a variety of devices mounted therein so, from the space point of view, it is difficult to mount a heater having such a large-diameter rotor. Thus there is a demand for the development of a heater which has an elongated shape and which can be disposed laterally along an engine.